Track and field is a sport in which athletes compete in running, jumping, and throwing events. Two events that combine running and jumping are known as the hurdles. In the hurdles, the athletes run in designated lanes and jump over spaced apart hurdles in between the start and finish. A hurdle consists of a base having two legs, two uprights, and a horizontal gate board (sometimes spelled “gateboard”). In the first hurdle event (commonly known as the high hurdles), athletes run about 100 meters and jump over relatively high hurdles. In the second hurdle event (commonly known as the low or intermediate hurdles), athletes run about 400 meters and jump over lower hurdles.
A hurdle is designed to tip over if the athlete contacts it. The force at the gate board required to tip the hurdle over is commonly known as its pull over weight. The pull over weight is a function of the height of the hurdle. Other things being equal, the pull over weight decreases as the height of the hurdle increases. Most hurdles contain added counterweights in the base to achieve the desired pull over weight. To maintain a constant pull over weight as the height of the hurdle changes, many modern hurdles incorporate counterweights that move in the legs of the base. As the height of the hurdle increases, the counterweights are moved further away from the uprights and, as the height of the hurdle decreases, the counterweights are moved toward the uprights. In some hurdles, the counterweights are moved manually. In other hurdles, the counterweights are connected mechanically to the gate board so that they move automatically as the gate board is moved.
The height of the hurdle in each of the hurdle events varies depending upon the age and sex of the athletes. For versatility and economy, most hurdles are adjustable in height. Adjustable hurdles contain a gate board that is attached to movable gate tubes (also known as risers) that telescope inside or outside the stationary uprights. Either the uprights or the gate tubes (whichever is outer) contain spaced apart vertical bores in their outer surfaces. One of the simplest height adjustment systems consists of a detent pin that is biased outwardly. For example, Zody, U.S. Pat. No. 5,352,057, Oct. 4, 1994, discloses an adjustable height hurdle having a detent pin in each inner upright that extends through a selected bore in each outer gate tube. Adjusting the height of the hurdle requires a person to bend down over to reach the detent pins.
More ergonomic hurdle height adjustment systems contain a vertical actuator with a distal pin that extends through a selected bore in the upright and a handle (sometimes referred to as a trigger or button) that extends out of each gate tube. The vertical actuator is typically biased in one direction by a spring to force the post into the bore. Squeezing, depressing, or otherwise moving the handle moves the member and disengages the post from the bore. A variety of height adjustment systems are used in hurdles. As examples, a mechanism with a manipulator and latch is disclosed in Dellinger et al., U.S. Pat. No. 4,749,187, Jun. 7, 1988; a mechanism with triggers and contiguous trigger tubes is disclosed in Watry et al., U.S. Pat. No. 7,438,668, Oct. 21, 2008; and a mechanism with a locking pin and a tension spring is disclosed in Lindstrom, U.S. Pat. No. 8,968,157, Mar. 3, 2015.
A major problem with conventional adjustable height hurdles with automatic counterweight systems is that dirt and water can enter the interior of the hurdle through the external bore holes and interfere with the counterweight system. Accordingly, there is a demand for an adjustable height hurdle without external bores in the uprights.